Relay



Dec. 21, 194s.

Filed nay 1e, 1944 WITNESSES:

F. C. IGLEHART RELAY 2 Sheets-,Sheet 1 ATTORNEY Dec. 21, -194s.

F. c. IGLEHART 2,456,945

RELAY Filed lay 16, 1944 2 Sheets-Sheet 2 wlTNEssEs: INVENTOR g Ferdz'nandC/giearz' cui* u* 'M BY flu-(22 ATTORNEY @Rented Dec. 21, 1948 OFFICE RELAY Ferdinand C. Iglehart, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Appllcltion May 10, 1944, Serial No. 535,835

l 'i Claim. My invention relates to shockproof contactors and, more particularly, to electric overload relays of shockproof design.

It is essential on board oi war vessels, mobile hoisting or shoveling equipment and other locations where impact shocks and severe vibrationsA are to be expected that the contactors of electric control devices are prevented from performing uncontrolled operations. For instance, the overload breakers and relays of electrical control equipment aboard ship must stay closed during normal operating conditions of the electric circuits to be controlled even if they. are subjected to shocks and impacts caused by gunfire.

It is known to render contactors shockproof by designing their movable parts as statically and dynamically balanced masses which, when in operation, rotate about their balanceaxis. However, such a design is often inapplicable or impractical. It is further known to provide electric contactors with latching devices which contain a movable inertia weight for moving a latch into the path of the movable contacter assembly in response to the occurrence of shock forces. Such inertia-controlled auxiliaries rendefr the contactors more l, complicated and involve the disadvantage that they prevent also an intended operation of the contactor during the periods of persisting shock forces. This is especially undesirable in the case of overload relays because it may prevent these relays from interrupting the current at the proper moment.

It is an object of my invention to provide a contacter, especially an overload relay oi theI iatched-in type, which is shockproof in accordance with the above-mentioned requirement but requires neither a balanced design of its .individual movable parts nor an additional inertiacontrolled latch.

Another object allied to the foregoing is to provide a shockproof contactor of especially simple design and small size.

It is also an object of my invention to provide a shockproof overload relay which can readily be adjusted orcalibrated for difierent current ratings.

A further object of the invention in conjunction with any of the foregoing is .to devise a thermal overload relay that is not only protected from disturbances due to shock but remains also substantially unaffected by changes in ambient temperature as regards the accuracy of its tripping operation. v

In order to achieve these objects, my invention in one of its aspects consists in a con- (Cl. 20o-118) tactor in which a contact controlling part is movable between two positions and biased for motion toward one of these positions, the movable part being straddled by two latch members which, under normal conditions, abut against a stop face oi the movable part and thereby prevent it from moving under its bias.l The two latch members are so disposed that they have to move away from the movablepart in opposite directions in order to effect a release, and this opposite motion is produced by a current-responsive electric control element. f

According to another feature of my invention, the two just-mentioned latch members consist of bimetal strips which extend substantially in parallel to each other and are heated in accordance with an electric load current so as to deilect simultaneously away from the movable part.

In another aspect of my invention. two bimetal strips, as just mentioned, are mounted on a carrier which is displaceable towards and away from the movable relay part to be latched by the strips. A displacement of this carrier has the effect of changing the distance between the stationary mounting of the latching strips and their points of engagement with the latched-in part. Consequently, the distance of angular deflection of these strips caused by a given current intensity is also changed. As a result, the rating of the relay can be adjusted or calibrated by displacing the strip carrier.

According to still another feature of my invention, a compensation for changes in ambient temperature is provided by means of auxiliary bimetal strips which act on the above-mentioned latching members or latching strips so as to vary their releasing deflection in dependence upon variations in ambient temperature.

The above-mentioned objects and features of' my invention as well as other characteristics thereof will be apparent from the following description of the embodiments illustrated in the drawings.

Figures 1 through 4 of the drawings refer to the same embodiment of a shockproof overload relay. Fig. 1 is a top view, Fig. 2 is a cross section taken along the line denoted in Fig. 1 by II--II, Fig. 3 is a bottom view, and Fig. 4 is a frontl view.

Figs. 5 through 8 represent a second embodiment of the invention. Fig. 5 is a top view. Fig. 6 is a lateral sectional view taken along the plane denoted in- Fig. 5 by the line VI--VL Fig. 7 illustrates ai lateral view corresponding 3 to Fig. 6 but showing the exterior of the relay. FIB. 8 shows a cross-section taken along the cut denoted in Fig. 7 by the line VIII-VIII.

The overload relay according to Figs. l through 4 has an insulating base or supporting structure II consisting for instance of molded material. A cavity I2 of base II contains a strip carrier I3 which has an extension I4 guided in a groove along the bottom of cavity I2. The carrier I3 is displaceable within the cavity and along the just-mentioned groove and has an elongated opening traversed by a setscrew I which permits fastening the carrier Il in any selected position within its range of displacement. Two bimetal strips I4 and I1 are firmly mounted on the carrier Il. They extend substantially in parallel to each other and straddle the top portion I8 of a plunger Il which is mounted in a bore of the base II and axially displaceable relative to the base. An insulating abutment 20 of plunger I5 rests against a resilient contact member 2I which, in the position according to Fig. 2, is in engagement with another resilient contact member 22 so as to close the circuit to be controlled by the relay. 'I'he contact members 2| and 22 are mounted on rigid terminals 24 and 25, respectively, which are molded into the base II. The contact members 2| and 22 exert a bias on plunger Il tending to move it towards the left (Fig. 2). However, a stop face formed by a flange 21 of plunger I8 abuts against the edges of bimetal strips Il and I1 and prevents the plunger from following this biasing force.

A heating element 2,8 is arranged within the cavity I2 and between the two strips IB and I1. It consists of an insulating carrier and a resistance wire mounted thereon and is provided with terminals 29 and 30 which are removably attached to the insulating base II. For different current ratings, the heating element may be replaced by a correspondingly diilerent one. For instance, for larger current ratings the heater may consist of resistance sheet material so formed that the terminals 29 and 50 are an integral part of the heater proper. The arrangement of the heater along and between the two bimetal strips secures a highly emcient heat transfer.

When the circuit connected to the heater terminals 2l and III is deenergized, the strips I6 and I1 are cold and press from opposite sides against portion IB of the plunger I8. When the circuit is energized and the current below the rated tripping value. the strips I6 and I1 are heated so that they reduce somewhat their pressure on the plunger and may slightly deflect in opposite directions away from the plungerwithout moving out of engagement with flange 21. Upon occurrence of an overload of suillcient intensity and duration, a further divergence of the bimetal strips occurs until they move clear of the ange 21 and thereby release the plunger Il. 'I'he plunger is now moved towards the left (Figs. 2 and 4). After a limited initial motion of contact member 22, it abuts against a stop I0 formed by the insulating base II in its rear cavity 23. while the contact member 2| is free to continue its motion. As a result, the contact between members 2| and 22 is interrupted. In the interrupting position of plunger I9, iiange 21 lies between strips I8 and I1 and hence prevents the strips from moving back into their original position while the strips are cooling down to normal temperature. In order to reset the relay,

assaut the plunger portion I8, serving as a push button, is depressed so that flange 21 is returned into the illustrated position. The bimetal strips I8 and I1, if cooled sufficiently, will now snap into the original position and again latch the relay.

If the relay, or the panel on which it is mounted, is subjected to shock or vibration, the shock or vibratory forces may be transmitted by base II to plunger I9 as well as to strips Il and I1. Any component of these forces acting on the plunger in its axial direction cannot cause an opening of the contacts because the opening motion of the plunger is blocked by the latching effect of strips I8 and I1. Any component of a shock force tending to move one of the strips Il or I1 in its releasing direction acts usually in the same direction on the second strip and hence tends to move this second strip towards its latching position. In other words, while the two strips in order to release the relay must be moved in opposite directions, the shock forces are as a rule unidirectional at any given instant and hence not apt to cause a release.

The deflection of the bimetal strips II at the point of engagement with the movable plunger under a given current load, depends on the distance of this point from the stationary mounting of the strips. Consequently, the rate of tripping current can be adjusted or calibrated by loosening the screw I5 and displacing the carrier I3. A displacement of the carrier and bi metal strips in the upward direction. referring to Fig. 1, decreases the rated current since less heat input is required to produce a given defiection at the latching point of the strips. Inversely, a downward displacement of the carrier increases .the rated current. As shown in Fig. i, the base II is preferably provided with a scale calibrated in per cent of rated current. I

The overload relay, according to Figs. 5 through 8, involves the same shockproofing principle as the relay previously described, but diers therefrom by providing for a compensation of ambient temperature variations as regards their effect on the rating and accuracy of the tripping operation. The embodiment according to Figs. 5 and 8 is further provided with adjusting or calibrating means different from those of the above-described overload breaker.

Referring to Figs. 5 through 8, an insulating base 4I has two cavities 42 and 53 at opposite sides. The cavity 42 contains a carrier 42 which forms part of a rigid holder structure 44. This structure is firmly attached to the base 4I. Two bimetal strips 46 and 41 have one end nrmly mounted on the carrier 43 and engage the top portion 48 of a plunger 49 which is mounted in the holding structure 44 for axial motion relative thereto and carries an insulating button Il for actuating two Contact members 5I and 52. These contact members are located within the rear cavity 53 of base 4I and mounted on two respective terminals 54 and 55. The base 4I has a projection 4D for limiting the spring-biased motion of contact member 52. A flange 51 of plunger 4l serves as a stop and is engaged by the denecting ends of strips 46 and 41 so that the plunger is normally prevented from moving under the bias produced by the contact members 5I and l2. A heater 58 is mounted between strips 4i and 41 by means oi terminals 59 and 50.

As far as described in the foregoing, the relay is designed and operative similar to the first-described embodiment and is shoekproof for the same reasons as set forthdn the foregoing,

In order to provide for ambient temperature compensation and also for the purpose of calibrating the relay, two compensating bimetal strips 18 and 11 are mounted in a slanted external groove on opposite sides of the insulating base 4I. Each of these strips has one -end provided with insulating buttons 1I and 1I, respectively. The base 4I has a transversal bore which contains two nuts Sil and Il, respectively, in engagement with two oppositely threaded portions I2 and 83 of an adjusting screw and are biased by helical compression springs 84 and Il, respectively, serving to eliminate dead play in the threaded engagement. Nut ll is riveted to the compensating strip 11 while nut Il is similarly attached to strip 18. 'I'he portion I2 of the double screw carries a calibrating disk Il. A projection 81 of this disk facilitates adjusting it to a desired angular position in accordance with calibrating indicia marked on the disk. A clamping screw Il serves to secure the disk Il in any selected position.

The heat insulating buttons 1I and 19 are so located in the path of deflection oi' the latching strips 48 and I1 that they exert an inward pressure on these strips as the latter approach their tripping position. This force is greater or smaller, depending upon the temperature and deflection o! the compensating bimetals 16 and 11 under the influence of the surrounding air. The buttons 1I and 19 are adjusted so that they just touch the latching strips 4l and l1 in their tripped position at the coldest air temperature-at which a compensation is to be effected and with the adjusting disk 86 set at 100% rated current. Ii' such an adjustment is infeasible or inconvenient to perform when assembling the relay in the factory. some other inter-relationship of temperature, percentage or rated current and distance of the buttons from the latching strips may be chosen in accordance with a computed or tested characteristic oi' the bimetallic elements. After adjusting the buttons 18 and 1l, they are soldered in place.

When manufacturing therelay, the bimetal strips 46 and 41 may be ground after being riveted to the carrier 43. Since the trip rod 49, which may also be ground, issecured to the rigid holding structure 44 rather lthan to the insulating base 4I, the entire strip, holder, and plunger assembly may be calibrated as a unit .by placing it in a bath of controlled temperature before the carrier 43 is rigidly joined with the structure Il, and sliding the carrier 43 forward `or back along the structure 44 or rotating it until a simultaneous trip'- ping of the two bimetal strips is obtained. The screw 6i (Fig. 6) for .fastening the carrier 43 'to the structure 44 is then tightened. The carrier 43 and the structure 44 may then be soldered or brazed together before mounting the calibrated assembly on the insulating base 4i.

Being aware of the fact that contactors according to my invention can be modified in various respects by those skilled in the art on the basis Y of the foregoingdisclosure and without departing from the objects and essence of the invention, I wish this specification to be understood asillus'trative rather than in a limiting sense,

I claim as my invention:

1. A thermal relay comprising a support, contact means mounted on said support, a plunger member movably arranged in said support for controlling said contact means and biased for arranged substantially in parallel to motion in a given axial direction and having radially extending stop means, two bimetal strips each other and straddling said member for engaging said means when cold in order to hold said member against its bias. said strips being mountedior moving in opposite directions radially away'from said member when heated, and current responsive heating means ,mounted on said support separate from said strips and disposed between said strips for heating both strips substantially equally for causing them to release said member in response to an overload current, and an adjusting device disposed for varying the heat-responsive'radial travel of said strips relative to said member in order to calibrate the relay for a given current rating and having a part displaceably mounted on said support so `that the position of said part is indicative of said current rating said device being associated with both said strips so that said radial travel of both said strips is changed simultaneously by a positional change of said part.

2. A thermal relay comprising a support, contact means mounted on said support, a plunger member axially movable in said support and biased for motion in one axial direction, said member` having radially extending stop means, a holder displaceable in said support toward and away from the axis of said member, two bimetal strips each having one end attached to said holder, said strips being arranged substantially in parallel to eachother and straddling said member for engaging said means when cold in order to hold said member against its bias", said strips being mounted for moving in opposite directions radially away from saidlmember and stop means when heated, and current responsive heating means disposed between said strips for heating both substantially equally for causing them to release said member in response to an overload current.

3. A thermal relay comprising a support hav ing two cavities at two opposite sides respectively and forming a partition which separates said cavities and has an opening extending between said cavities, contact rmeans mounted on said support in one of said cavities, a plunger member axially movable in said supportand extending through said opening from one t'o the other cavity, said member having a radially extending stop means and being biased for motion in-one of its axial directions, two bimetal strips in said other cavityv arranged'substantially in parallel to each other and straddling said member for engaging said stop means when cold in order to hold said member against its bias, said strips being mounted for moving in opposite directions radially away from said member when heated, and current responsive heating means mounted on said support separate from said strips and disposed between said strips for heating both strips substantially equally for causing them to vrelease said member in response to an overload current.

4. A thermal relays comprising a support having two intercommunicating cavities at two opposite sides respectively, contact means mounted on said support in one of said cavities, a plunger member axially movable in said support and extending from one to the other cavity, said member having a radially extending stop and being biased for :notion in one of its axial directions, a holder slidably arranged in said other cavity so as to be displaceable toward and away from the axis of said member, two bimetal strips each having one end attached to said holder, said strips being arranged substantially in parallel to each other and straddling said member lor engaging said stop when cold in order to hold said member against its bias, said strips being mounted for movingin opposite directions radially away from said 'member and stop when heated, and current responsive heating means disposed between said strips for heating both substantially equally for causing them to release said member in response to an overload current,

5. A thermal relay comprising contact means, a plunger member movably arranged for controlling said contact means and biased for motion in a given axial direction and having a radially extending iiange, two bimetal strips straddling said member for engaging said iiange when cold in order to hold said member against its bias, said strips being mounted for moving in opposite directions radially away from said member and flange when heated, and current responsive heating means associated with said two strips 4for causing them to release said member in response to overload current, and two compensating bimetal strips extending transversely oi' said first strips and having a part disposed in the path of their heat responsive motion respec-v tively, said compensating strips being exposed to ambient temperature for impeding the releasing motion of said rst strips so as to substantially, compensate the effect of changes in ambient temperature on the current responsive release operation.

6. A thermal relay comprising contact means. a plunger member movably arranged for controlling said contact means and biased for motion in a given axial direction and having a radially extending ange, two bimetal strips straddling said member for engaging said flange when cold in order to hold said member against its bias, said strips being mounted for moving in opposite directions radially away from said member and ilange when heated, and current responsive heating means associated with said two strips for causing them to release said member in response to overload current, and two compensating bimetal strips extending transversely of said nrst strips and having a part disposed in the path of their -heat responsive' motion respectively, said compensating strips being exposed to ambient temperature for impeding the releasing motion of vsaid tlrst strips so as to substantially compensate the eii'ect of changes in ambient temperature on the current responsive release operation, and a manual calibrating device connected with said two compensating strips for varying the distance of said parts from said respective first strips.

1. A thermal relay comprising a support having two intercommunicating cavities at two op posits sides respectively, contact means mounted on said support in one oi' said cavities, a plunger member axially movable in said support and eX tending from one to the other cavity, said member having a radially extending stop means and being biased for motion in one of its axial directions, two bimetal strips in said other cavity arranged substantially in parallel to each other and straddling said member for engaging said stop means when cold in order to hold said member against its bias, said strips being mounted for moving in opposite directions radially away from said member and stop means when heated, and current responsive heating means disposed between said strips for heating both substantially equally for causing them to release said member in response to an overload current. and two compensating bimetal strips of opposite heat responsive deflection mounted on opposite sides oi said support exteriorly oi' said cavity and transversely of said ilrst strips and having each a part disposed in the path ot heat responsive. motion of one or said respective iirst strips for impeding said motion in dependence upon changes in ambient temperature, and a caiibrating device having a shaft extending through said support and provided with two oppositely pitched threads in engagement with said compensating strips respectively for adusting the distance of said parts from said respective first strips when. said shalty is rotated.

FERDINAND C. IGLEHART.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS l Number Name Date 926,584 Morris et al. June 29, 1909 1,232,458 Cavanagh July 3, 1917 1,294,045 Cavanagh Feb. 11, 1919 1,683,132 Hall Sept. 4, 1928 1,795,211 Horst Mar. 3, 1 931 1,838,664 Dubilier Dec. 29, 1931 1,914,529 Rich June 20, 1933 1,939,194 Angell Dec. 14, 1933 2.302,71? Rostoker Nov. 24, 1942 2.401,005 Lindstrom et ai May 28, 1946 FOREIGN PATENTS Number Country Dato 443,870 Germany --.p May 12, 1927 

